Hi guys.. I have a new car coming soon, with a stroker holden V8 in it.. probably running fairly high compression (10:1) as it only runs on premium unleaded.. How can I lower the compression without changing pistons? as it's already got a set of forgies in there apparently.. Would a thicker head gasket be the go? How do I find out how big to mkae it to drop it to the desired compression ratio? will this make it more likely to choof a gasket under high load?

Morgz, You finally made it over to the dark side, about frigging time. I believe the easiest way in your situation would be to use thicker copper head gaskets. If your running boost into it you should probably upgrade to copper anyway. Not sure exactly how to work out your compression ratio. I think if you raise the standard gasket height by around 50-60 thou it should lower your compression from 10:1 to 9:1. I could be completely wrong you need to speak to an engine build like Matty, he will tell you for sure.

Found it, don't ask me how to use it though.... http://www.corral.net/tech/compress.html

Ahh your a legend scott! Yeah I couldn't resist the dark side... I'll give you a run hopefully when your next in Ballarat.. Some original photos have not been recovered yet.

nah you'll always be limited.. the engine is running currently im guessing a 45thou inch gasket approximately at the moment.. yes u can lower compression by running a bigger gasket but basically the taller u go the weaker they get.. you would need probably a 90thou gasket or something to get it in the mid to low 9s, even then u will be limited by how much boost u can run. IMO its never a good idea to try and turn a worked n/a motor into a boosted terror, better off stripping it down removing the weaknesses.

Hmm, yeah I can settle for less boost.. it's not a quarter machine or anything like that... If I can run maybe 8psi I'd be happy.. should be enough to make around 300rwkw.. the right cam and some headwork would help too.. Depends on the cost invloved of fitting lower comp pistons... if it's not worth it.. i'd wait until it need to be pulled down and then do the whole lot.

mate with v8s u dont need much cam or heads, keep em stock even and 300rwkw is a breeze depending what blower/turbo u use, ESPECIALLY with a stroker. u will prob be able to squeeze more psi out of it depending... whats the car morgo tell us more lpg? what forced induction u talking about? Some original photos have not been recovered yet.

not lpg im tipping.. and a blower im guessing.. on a 5L injected commodore.. put the pistons in yourself you lazy POS

a stroker holden..and ur talknig cam and heads.. u should prolly make 300 kw without forced induction...

get the combustion chamers made bigger , engine shop can do a nice job on the heads making them bigger or u can have a hack your self , best to get them to do it they will cc the heads to make sure its all sweet

If you change to a thicker head gasket you will also need a thicker intake manifold gasket so that your manifold sits properly between the heads.

hmm awesome replies guys... thanks a million! Yeah it's currently got a 215i stroker in it, forgies, exhaust and some some other goodies.. I'll get it dynoed and find out how healthy it is and go from there.. It will be running petrol (bp ultimate only while in my hands). Blower wise I wanna try one of the Vortech series.. depending on funds, a V7 YS Trim like rob vickey did on his DCEIVE ute... I loved that setup Will see how it all goes together over the coming months, and decide whats gonna be the best way to get some reliable power out of it. Some original photos have not been recovered yet.